I. Field
This generally relates to communications. More particularly, the invention relates to communications of short-range networks serving-specific purposes.
II. Background
In some WLAN systems, including wireless personal area-networks (WPANs) such as those established under IEEE 802.15 protocols for personal area networks (PANs), a host function is assumed by self-selection.
A WPAN is sometimes called a piconet. As used herein, the terms “WPAN” and “piconet” are used interchangeably. In a typical piconet, one or more devices (DEVs) are linked together. In an arrangement where more than one DEV is present in the piconet, one of the devices is identified as the piconet controller (PNC) which assumes the function of coordinating other DEVs within the piconet. The criteria to be designated as the PNC are set forth in IEEE 805.15.3. It should be noted that the description of IEEE 802.15 protocols is for clarity of explanation and is not intended to be limiting as to the scope of the invention.
One example of an IEEE 802.15 architecture is given by the IEEE 802.15.3a wireless USB specification. The IEEE 802.15.3a standard wireless USB (WUSB) specification does not support the use of hubs. Instead, WUSB also supports dual-role devices, which in addition to being a WUSB client device, can function as a host with limited capabilities. The host role is taken by a WUSB device that is capable of performing the host functions and does not see another host within a local network. The WUSB device assuming the host function establishes a PAN.
Equipment components can be interconnected wirelessly. For example, in a computer system, various peripheral devices can be linked together via a wireless personal network (WPAN). A WPAN is very often designed to be short-ranged in nature serving one or more special purposes. Standards for WPANs are published, for example, in the IEEE 802.15.3, entitled “Wireless Medium Access Control (MAC) and the Physical Layer (PHY) Specifications for High Rate Wireless Personal Area Networks (WPAN)”.
While there are some circumstances in which the PAN would not have any function without the particular device which assumed the host role, there are other instance in which it is desired to maintain network connections regardless of whether the original host remains on-line as part of the network. According to the IEEE 802.15.3a specification, if a host device, known as a piconet controller (PNC) drops out, the PAN (network) collapses and another device capable of function as a host may establish a new PAN. This results in a network interruption until the new PAN is established, and also results in wireless connections terminating and then becoming reestablished.
There is a handoff process stated in IEEE 805.15.3. That is, the designated PNC has the option of handing over control of the piconet to another DEV. For example, when there is another device more capable of being the PNC, or the currently designated PNC intends to leave the piconet, the handover procedure can be carried out.
Heretofore, no provision has been made in a scenario when the current PNC suddenly stops communicating with other DEVs, for example, in a power failure, a hardware malfunction, a sudden turnoff of the power switch, or the current PNC suddenly moving away from the piconet without warning. When that occurs, timing synchronization among DEVs would be disrupted. The piconet can be restarted, and can then attempt to designate another DEV as the PNC; however, restarting and resetting the piconet are relatively time-consuming. Additionally, critical data could be lost which may not be recoverable during the piconet interruption process. The same unwanted consequences can also occur even if a handoff candidate has been designated by the current PNC. For instance, when both the current PNC and the designated PNC candidate suddenly move away, communications among DEVs of the piconet would also be jeopardized.